Cryptographic telegraph system



Aug. 13, 1946.

K. E. FrrcH E TAI.

CRYRTOCTRAPHIC TELEGRAPH SYSTEM 3 Sheets-Sheet l Filed March 18, 1942 A15'. FITCH v WWA/Twas. Locke ATTORNEY Aug. 13, 19MB. K. E. FrrcH z-:TAL l 2,405,569 CRYPTOGRAPHIC TELEGRAPH SYSTEM v Filed March 18', 1942 u 3 Sheets-Sheet 2 a l-HI- F G Z REPEA TER K. E. F/ rcH /NVENTORS @Amc/(E ATTORNEY s shets-sneet s K. E. FITCH ETAL CRYPTOGRAPHIC TELEGRAPH SYSTEM Filed March 18, 1942 ATTORNEY Aug. '13, 194s.

Patented Aug. 13, 1946 CRYPTOGRAPHIC TELEGRAPH SYSTEM Karl E. Fitch, Summit, N. J., and George A. Locke,

Glenwood Landing, N. Telephone Laboratories, Incorporated, New

Y York, N. YV., a corporation of New York Application March 18, 1942, Serial No. 435,178

34 Claims. l

This invention relates to telegraph apparatus and systems and particularly to a cryptographic or cipher system.

Systems of this general type are exemplified by a number of patents in the prior art, such as Patent 1,310,719, granted July 22, 1919, to G. S. Vernam, which discloses a transmitting distributor for transmitting signals evolved by the interaction of message signals set up by a keyboard transmitter and cipher signals set up by a tape sensing mechanism, and a receiving distributor for delivering to a live-magnet receiving printer signals evolved by the interaction of signals impressed on a telegraph line, whether by local or remote transmitting distributor, and cipher signals set up by the same tape sensing mechanism. Another patent which shows a cipher system employing notched discs instead of a tape controlled sensing mechanism for setting up the cipher signals is British Patent 442,602 of Creed and Company, Ltd., led August 17, 1934, accepted February 12, 1936.

An object of the present invention is to initiate code signals indicative of message material by means of keyboard controlled contacts mechanically actua-ted for successive impulses and simultaneously to modify said signals impulse by impulse according to cipher code signals.

Another object of the invention is to modify l ciate the signal modifying instrumentality from the signal initiating and receiving devices upon the transmission or reception of a break signal.

The invention features a perforated tape controlled signal generator operable in start-stop manner and producing start-stop signals for modifying received signals or signals initiated for transmission The invention also features a repeater associated with a telegraph signa1 receiving and trans mitting station which includes a reversing relay, controlled in accordance with the reception of signals or the initiation of signals for transmission, for routing received signals into the signal modiiier from which modied signals are impressed upon the receiving recorder and for routing signals initiated for transmission into the signal modier from which modied signals are impressed upon the telegraph channel for transmission.

- In accordance with the preferred embodiment nf, ull

Y., assignors to Bell of the invention, the system includes a pluralit of signal transmitting and receiving station which may be interconnected over telegraph line through a central oce exchange which ha switchboard facilities. Each station has a receiv ing telegraph printer and a keyboard controlle transmitter and each station may have in addi tion to or in lieu of the keyboard transmitter perforated tape controlled transmitter. The re oeiving printer and the transmitter are connecte to a repeater to which the incoming telegrap line is also connected. There is also associate with the repeater a cipher unit which consist essentially of a signal responsive input relay, a: output relay, and a tape controlled signal gen erator. The signal generator has in storage substantial quant-ity of previously prepared tap containing signal perforations representing char acters preferably in an unintelligible sequencr Upon the operation of the keyboard transmitte to generate signal impulses representing a char acter of a message the signaling impulses ar applied through the repeater to the signal re sponsive input relay of the cipher unit. Th signal generator of the cipher unit is started i response to the start impulse of the signal initiat ed by the keyboard to generate a ciphering cod signal under the control of the storage tape i timed relation to the response of the input rela to the impulses initiated by the keyboard tran: mitter. The output relay is controlled joint] by the input relay and by the tape cor trolled ciphering signal generator in such marl ner that impulses of one type, such as spacin; shall be generated in response to like impulse and impulses of another type, such as mark ingY shall be generated in response to unlik impulses simultaneously received by the inpi relay and generated by the tape controlled sign: generator. The signals generated by the outpi relay are impressed through the repeater on tl: telegraph line. A relay associated with the rf peater is operable in response to the initiation t signals at the keyboard transmitter for routin the signals to the input relay of the cipher un rather than directly through the repeater to tk telegraph line.

Signals received over the telegraph line entf the repeater. and the routing relay operates i response to the receptionl of signals, as distir guished from the initiation of signals, to rou the received signals to the input relay of tl cipher unit. The received signals are those ger erated by the output relay of cipher unit attr Station from which the signals are being receiver the tape in the tape controlled signal genors at both stations is identical and is ad- :ed one step for each character transmitted eceived so that identical signals are always ented to the tape sensing elements of the al generators. The signals received and api to the input relay of the cipher unit control output relay of that unit jointly with the I, controlled signal generator to reproduce the sage signal initiated by the remote transler. This deeiphered signal is applied throughV repeater to the printing recorder.

)r a complete understandingv of the invention rence may be had to theV followingI detailed ription to be interpreted. in the light of the mpanying drawings wherein:

g. 1 is a schematic circuit diagram showing. message transmitter and recorder and thev .er unit in accordance with the present; innon;

g. 2 is a schematic circuit diagram showingv repeater according to the-preferred embodi- .t off the invention;

Lg.. 3 is a diagrammatic representation of a plete communicationsystem including a plu- 1y of stations of the type shown inFigs. land be selectively interconnected through a cen oii'ice exchange; and ig. 4. is a schematic circuit' diagram showing a lined form of cipher unit. eferring now to the drawings and particularly ig. 1, the apparatus contained within the :en line rectangle II represents a combined eiving telegraph printer andL keyboard trans- :er which. may be ofthe type shown in Patent 4,164,` granted April 18, 1933, to S. Morton tl. The disclosure of this patent is incorpo- :d herein by reference as part of the present :icatiom In Fig. 1 the printer is indicated ,bolically by the selector magnet I2 and the Joard transmitter for4 transmitting start-stop nutati'on code signals is represented by the Ismitting contacts, I3. Theselector magnet I2 onne'cted tothe sleeve terminals of a double 5 I4 and the transmitting contacts I3 are con- :ed to the tip contacts of the double plug I4. double plug I4, is adapted, to be inserted into :s I1Y and L8 or 2Il and 22 of a repeater shown rig` 2. hev pair of jacks I1 and I8 andthe pair of s 2l and 22 represent the station side of the eater; The opposite side which is the line of the repeater is entered by telegraph line :luctors 23 and 24.v Line. conductor 23 is con- ;ed through the winding of a break relay 26 through the upper or operating winding of a .r line receiving relay 21 from which. a circuit be traced through conductors 28 and 29, tip tact spring of jack. I1 and contact spring :h it' engages when plug I4 is not inserted in :s I1 and I8, conductors 3| and 32, normally' edv contacts ofv a relay 33which theright-hand ature` isoperable to open, conductor 34., arma- I and marking contact of the line sending y 36 which is also a polar relay, and. conbor 31 to telegraph line conductor 24. From it will be apparent that when plug I4 is4 not rted into jacks I1 and i8, the telegraph line iuctors 23, and. 24 terminate in the.. repeater heF loop circuit just traced without any local 'ce of signaling current.,A from which it-follows :telegraph battery is connected at the remote of the telegraphline to provide current for aling. The lower or biasing winding. of relay ias. one. side connected through resistors,l 38

I spacing position but in the rest condition of the apparatus current supplied over the telegraph conductors 23 and 24 and through the operating winding of relay 2.1 overcomes the effect of the biasing winding andholds the armature in marky ing condition.

Upon the insertion of plug I4 into jacks I1 and I8, conductor 3 I4 becomes disconnected from conductor 29 at` thev tip contact spring of jack I1 so that the'loop circuit between relay 26 and the armature of relay 36 is broken. In its place a loop is completed. through` the, tip of. the upper plug,y transmitting contacts.. I3, tip of the lower plug, tip contact spring of jack I18 .and conductors 46` and 41 to line conductor 2L Upon the operation of transmitting contacts I3 under, the control of the keyboard transmitter,v theA loop which Yinterconnects line conductors 23A and 24 .is interrupted in correspondence withsignals tov be transmitted thus generating marking' and, spacing signals of current and nocurrent conditions respectively. When the loop 'is interrupted to pro.- ducea spacing condition,.current in the operating winding of relay-21 is` interrupted so that the biasing winding becomes effective to drive the armature to the spacingl contact.. The armature of relay 21 is connected through conductors 48 and 43' to the sleeve of jack I1 and thence through the. sleeve of the upper plug, selector magnet I2, sleeve. of the lower plug to the. sleeve of the jack I 8 which isconnected to ground. The marking contact of relay 21 is connected to the negative terminal of battery 5I, the positive terminal of which isA grounded, and the spacing contact is connected through conductor 52. and the upper winding ofa relay 53 to ground.. With. the armature of relay 21 engagingl its marking contact, current ows to energize selector magnet L2 which isV the marking condition. When the armature of relay 21 goes to spacing, the circuit of' selector magnet I2 is` grounded. at. both ends` so that. no current flows. through selector. magnet I2 or through the upper winding ot relay 53.4 This is the spacing condition of selector magnet I2.`

From the foregoing, it will be apparent that relay 21- serves as a line relay to control the operation. oil selector magnet. I2 in response to signals received over the telegraph line. comprising,` conductors. 23 and` 24 and also serves as a local repeating: relay to-repeat to magnet. I2 signals generated locally by the transmitting contacts I3. Itwill be noted that.y signals generated by the contacts I3 are impressed directly upon theline conductors` 23 and 214 and are not repeatedfor transmission purposes but only for home. record. purposes. ItV will also be noted that` the. system provides. for signal transmission in either direction over liner conductors` 23 and 24 but not tor simultaneous transmission in both directions.` The tipspring ofrjack I1 is mechanically but not electrically associated with.- a spring above` itwhich is engageable with a grounded contacti wheni plug I-4vis inserted in the-jacks I1 and` I8 and which is connected to one side of a lamp 52, the other side of which is connected to. grounded battery. Thus' wheny plug I4 isengaged with jacks I1 and I8, lamp 52 will be lighted to indicate that the type of message transmission hereinbefore described is available.

Referring now to the jacks 2| and 22, a circuit may be traced when plug I4 is not inserted in the jack from ground on the spring of jack 22 which is mechanically associated with but electrically isolated from the tip spring of that jack through the Contact which the spring engages when no plug is inserted in the jack, conductor 56, back contact and inner right-hand armature oi' relay 51, conductors 58, 59 and 60, lowermost contact spring and tip spring contact of jack 2l, which engages the lowermost contact when plug I4 is not inserted into jacks 2I and 22, conductors 6I and 62, inner left-hand armature and back contact of relay 51, conductor E3, upper or operating winding of polar relay 64, conductor 66, armature and marking contact of polar relay 61, and resistor 63 to the negative terminal of battery 69, the positive terminal of which is connected to ground. Current flows in this circuit in the direction to hold the armature of relay 64 on its marking contact. Conductor 56 is also connected to the sleeve of jack 22 so that when plug I4 is inserted into jacks 2I and 22, the circuit just traced is enlarged to include the selector magnet I2 and transmitting contacts I3, and extends from ground on the sleeve of jack 2! through the upper sleeve contact of plug I4, selector magnet I2, lower sleeve contact of plug I4, sleeve of jack 22 from which ground on the upper Contact spring is now disconnected, conductor 56, back contact and inner right-hand armature of relay 51, conductors 53 and 59, tip spring of jack 22, tip of the lower plug of double plug I4, transmitting contacts I3, tip of the upper plug of double plug I4, tip contact spring of jack ZI, conductors 6I and 52, inner left-hand armature and back contact of relay 51, operating winding of relay 54, conductor 65, armature and marking contact of relay 51, resistor B8, to grounded battery S9. From this it will be observed that When plug I4 is inserted in jacks 2| and 22, selector magnet i 2 is placed in series with transmitting contacts i3 so as to respond directly to perm-utational operation of the transmitting contacts, Whereas when the plug was inserted in jacks I1 and I8, signals genera-ted by the transmitting contacts I3 were repeated to selector magnet I2 by relay 21.

The tip spring of jack 2i mechanically operates two contact springs to complete by means of the uppermost of these'springs a circuit from ground on the left-hand armature of a relay 1I, through its back contact, conductor 12, closed upper contacts operated by the tip spring of jack 2|, lamp 13, to grounded battery, thus lighting the lamp to indicate the type of transmission that is now available, namely, cipher transmission. At the lower of the two sets of contacts closed by the operation of the tip contact spring of jack 2I, a circuit is prepared from the junction of resistors 39 and 39, through which current for the `biasing winding of relay 21 is supplied, over conductor 14, the closed contacts associated with jack 2i, conductor 15, back contact and left-hand armature of relay 33, and conductor 16 to normally open contacts 11 which are operable by a locking bail for the keyboard transmitter in a manner which will be described later, together with the function of the circuit just traced.

Upon the operation of transmitting contacts I3 to initiate the transmission of a code signal, the

circuit through the operating winding of rela 64 is opened for the start impulse and for eac spacing impulse and is reclosed for each markin impulse and for the stop impulse. The biasin Winding of relay 64 is energized in a circuit be ginning at the interconnected resistors SI an 82, the opposite ends of which are connected i negative battery 83 and ground respectivel; Resistors 3| and 82 form a potentiometer froi which the circuit extends through the -biasin winding of relay S4, conductor 55, armature c relay 61, which at this time is held on the mark ing contact, resistor 68 and battery B9. Th biasing winding of relay 64, as thus energize( seeks to move the armature to the spacing con tact but is prevented from so moving the arma ture when current flows through the operatin winding of the relay. However, upon the inter ruption of the circuit through theI operatin winding due to the permutational operation c transmitting contacts I3, the biasing winding c relay 64 becomes eiective to move the armatur to the spacing contact.

With the armature of relay 64 on the markins contact, a circuit may be traced from grounder battery 5I through the marking contact an armature of line receiving relay 21, conductor 48 and 84, middle right-hand armature and bac] contact of relay 51, conductor 86, marking con tact and armature of relay 64, conductor 81, xe contact and movable spring operable in make before-break manner by a contact spring mechanically operable by the tip contact spring o. jack I8, conductor 98, Xed contact and movablr front contact operable by the inner right-han( armature of relay 1I, conductor 39, operating Winding of polar input relay 9| of a. cipher unir (Fig. 1), to the potentiometer comprising resistors 92 and 93 and through those resistors tc the negative terminal of battery 94, the positiv( terminal of which is grounded, and to grounc' respectively. It is to be noted at this point thai the circuit just traced is interrupted at the makebefore-break contacts of jack I8 when plug I4 is inserted in the jacks i1 and I9 but that a substitute circuit for holding the operating winding of cipher unit input relay 9| energized, to hold its armature on the marking contact, is completed from the negative terminal of grounded battery 96 (Fig. 2) through resistor 91, conductor 98, the make contacts operable by the tip spring of jack I8, conductor 83, make-beforebreak contacts of relay 1I conductor 89, operating Winding of relay 9|, to resistors 92 and 93 in parallel.

The circuit from the battery 5I associated with the marking contact of relay 21 through the armature and marking contact of relay 64 and the winding of relay 9| is interrupted when relay 64 responds to spacing signals generated by contacts I3 and the armature of relay S4 leaves the marking Contact, and a substitute energizing circuit for relay 9| is completed from ground on the upper terminal of the middle Winding of relay 53 through that winding, conductor IBI to the spacing contact of relay 64 and through the armature of that relay and the previously traced circuit to the operating winding of relay S i. Due to the substitution of ground on the spacing contact for the negative battery connection on the marking contact and armature of relay 21, the flow of current through the operating winding of relay 9| is reversed. This current also traverses the middle Winding of relay 53 in a direction to move the armature of that relay from the leftd to; the: rightehand contact.. No current has i flowing through theA upper winding of relay nd conductor 52 because that conductor terates at the spacing contact of relay 21 and rdingly the operation of the armature of y 53 to its right-hand contact is unopposed. 'lower winding of relay 53 has one terminal` iected to the negative terminal of grounded ery |02 and the other terminal connected to right-hand contact of relay 53 from which a uit also extends through conductor |03, biaswinding of relay 61. and resistor |04 to the ative terminal of battery 69. No current s in this circuit with the armature of relay in. itsv left-hand contact becauseV batteries 09 |02 are in opposition. However, with the inded armature of relay 53' on its right-hand bact circuits in. parallel are established for lower winding of relay 53 to battery |02 andy the biasing Winding of relay 61 to battery 69. flow of current through the lower winding of ly 53 is in a direction to hold the armature on: right-hand contact. The flow of current augh. thev biasing winding of relay 61 is in a action to holdV the armature of that relay on marking contact so thatV it cannot be moved to cing regardless of reversals which may occur he operating winding. l,eferring now to- Fig. l, it will be noted that v armature of relay# 9| isoperable between rking and spacingV contactsY which are contedthrough resistors |06l and |01, respectively, ;he negative terminal of grounded battery |08 l to ground, respectively; The armature of ty 9| is connected by conductor |09 to one ner |0911 of a triangular bridge network which iprises one side or-arm containing resistor econd side or arm containing resistor ||2 and operating winding of polar output relay |3', l a third side or arm containing resistor |'|4. mthe point of interconnection of the operatwinding of relay ||3 and resistor' H4', desig- :ed as the bridge corner ||6a, conductor HS ends to a set of ve contacts of a` tapetrans iter distributor and these will be assumed to the spacing contacts. From the point of inconnection of resistors and ||2, designated bridge corner |I1a, conductorv |||1 extends to r other live contacts of the transmitter distribr and" these will be assumed to be the marking itacts. Phe tape transmitter distributor is somewhat iilar to aA tape controlled transmitter distrib- )r disclosed in Patent 2,055,567, granted Sep:-

nber 29, 1936, to E. F. Watson, andthe dissure of the Watson patent is incorporated reinby reference as part of the present speci'- ation. However, the distributor has a conside rbly diierent arrangement of signal generating ments, as will be described hereinafter.

Ihe distributor has a brush arm |2| Which is rried by a rotatable shaft |22 to which rotan is imparted from motor |23 through friction itch |24 and gears |26. A stop cam |21 is sered to shaft |22 and is arranged -to be arrestedl armature lever |28 of electromagnet |29 wheny e magnet is deenergized. Upon the energiza- )n of magnet |29, the end or armature lever 8 presented toward cam |21 is rocked out of :cking relation, to the cam whereby shaft |22 released for rotation. Brush arm 2| carries 8i4 ment insulated. from the main, body or thev ring andthe inner brush carried by brush arm |'2I is in engagement with the short segment when brush arm |2| is held at rest by the cooperation of armature lever |28 with cam |21, the segment may be called a rest segment. The outer segmented ring has a short segment which. is a companion to the rest segment of the inner ring and subtends the same angle. ImmediatelyI ahead of and behind the rest segment of. theA outer ring are short conductive segments which representV the start and stopy impulses respectively. The start segment is the first to beY engaged by the brush after leaving the rest segment and the stop segment is the lasti to be engaged by the brush before coming into engagement with the rest segment. The remainder or the outer ring contains five uniformly space-d short conductive segments which correspond to the five codeV impulses of a permutation code combination and these segments are connected to the five contact tongues |'3|, which are permitted to move into engagement with their upperor marking contacts when the sensing pins (not sho-wn) by which they are controlled encounter perfora-v tions in they tape |32, and are heldv in engagement with their lower or spacing contacts when their associated sensing pins encounter imperiorate portions of tape |32. The start and stop segments are connected to conductor HS which extends to the left-hand` side of the operating winding of output relay H3, as previously set forth. The inner ring of the distributor exclusive of the rest segment is connected by conductor i i3d through thelower winding of'input relay 9|,

which is employed as avrlocking winding, and through resistors |36 and |31' in parallel to the negative terminal of battery |39, the positive terminal of which is grounded, and to ground respectively.

With distributor brushY |2| in the rest position, the two rest segments are bridged by the vbrushes as previously stated and a circuit may be traced from ground on the positive terminal of battery |39V through theY battery, resistor il, winding of start magnet |29 oi the distributor, closed switch 44, conductor |49, inner and outer rest segments of the distributor, conductors |41 and |09, and armature of relay 9| where negative battery |03 on the marking contact normally opposes negative battery lll! and holds start magnet |29 deenergized but where ground connection is now applied through resistor |01 and the spacingv contact since it has been assumed that relay 9| has gone to spacing in response to the start impulse of a signal combination initiated by transmitting contact I3. Start magnet |29 therefore becomes energized over the circuit just traced and releases l the distributor brush i2@ for rotation.

o electrically interconnected brushes which v idge outer and inner segmented rings. The inner ring of the distributor is electrically ntinuous except for a short conductive seg- The brushes first encounter the start segment' where a circuit is completed from the potentiometer comprising resistors |39 and |91 through the locking winding of' relay 9|, conductor |34, innery ring and start segment of the distributor,

conductor H6 to bridge cornerl 59a and then in ing contact and through the locking winding of relay 9| in the direction to hold the armature of relay 9| on its spacing contact during the interval that the brush traverses the start segment, so that the armature of that relay cannot return to marking even if one of the transmitting contacts |3 should become closed for a marking impulse and restore current through the operating winding of relay 3| in the direction to restore the armature to the marking contact. Current in the locking winding of relay 9| is always paramount to current in the operating winding and the armature of the relay can be shifted under the control of the operating winding only when no current is flowing in the locking winding. Since currentV flows in the locking winding of relay 9| only during the brief interval that the brushes traverse a segment in the outer ring of the distributor, the locking winding will not prevent a marking or spacing pulse of normal length in the operating winding of relay 9| from operating the armature.

The armature of output relay ||3 is connected through resistor |43 and the lower or locking winding of output relay |`|3, and resistors |5| and |52 which form a potentiometer, the former being connected to the negative terminal of battery |53, the positive terminal of which is grounded.4 and the latter being connected to ground. Current through the holding winding of relay ||3 is always in the direction to hold the armature in engagement with the contact to which it has been moved and through which a holding circuit has been completed from the negative terminal of battery |49 on the marking contact or` from ground on the spacing contact, but current in the holding winding is subordinate to current in the operating winding so that upon a reversal of current through the operating winding the armature will be moved in spite of the holding current in the lower winding and a new holding circuit will be established tending to hold the armature in the new position. It is to be noted that current is always flowing through the holding winding of relay ||3 in one direction or the other, whereas current flows in the holding winding of relay 9| only when the distributor brushes are traversing a conductive segment in the outer ring, excluding the rest segment.

The armature of output relay ||3 is also connected through conductor |56, operating winding of relay 61 (Fig. 2) conductor |51, operating winding of line sending relay 36 to a potentiometer consisting of resistors |58 and |59, the former of which is connected to the negative terminal of battery 44 and the latter of which is connected to ground. With' the armature of relay |3 on itsspacing contact, current through the operating-windings of relays 61 and 36 is thus reversed. It has been set forth previously that upon the operation of the armature of relay 53 to its righthand contact, resulting from the initiation of signal transmission at transmitting contacts |3, the relay 61 became biased to hold its armature in the marking position so that reversals in its operating winding will not drive the armature to spacing. This is necessary in order to prevent relay 61 from reversing the biasing current for relay 64 and thus interfering with the operation of that relay under the control of transmitting contacts |3. It will be noted that the circuit of the biasing winding of relay 36 extends from the negative terminal of grounded battery |6| through resistor |62, conductor |63, biasing winding of relay 36 and conductor |64 to the left-hand contact of relay 53. Since the armature of this relay is now held to the right-hand contact vby current through the lower winding of the relay, therewill be no current in the biasing winding of polar relay 36 and the armature of relay 36 is controlled solely by the operating winding, moving the armature to spacing, which is a dead contact, when relay ||3 is spacing, and restoring the armature to marking when relay |3 is marking. The condition of the repeater circuit with respect to line conductors 23 and 24 just before the relay 36 is operated to spacing is that a previously described loop circuit is bridged across the line conductors 23 and 24 from conductor 23 through relay 26, the operating winding of relay 21, conductors 26 and 29, tip spring contact of jack l1 and contact now engaged by the tip spring contact, conductors 3| and 32, closed contacts controlled by the right-hand armature of relay 33, conductor 34, armature and marking contact of relay 36, and conductor 31 to line conductor 24. Upon the operation of the armature of line sending relay 36 to spacing position, this loop is opened, thus placing the line conductors 23 and 24 in spacing condition.

It will be noted that upon movement of the armature of sending relay 36 to spacing, current is interrupted in the operating winding of receiving relay 21. Reerence is again made to contacts 11 (Fig. l) the closure of which will connect ground over conductor 16, left-hand armature and back contact of relay 33, conductor 15, contacts of jack 2| now closed, conductor 14 and resistor 38 to one terminal of the biasing winding of relay 21. The opposite side of the biasing winding of relay 21 is connected to the potentiometer which comprises resistors 42 and 43, so that current flows in the opposite direction in the biasing winding of relay 21. The armature of relay 21 is thus biased to the marking position and will not go to spacing when relay 36 impresses a spacing condition on the line conductors. Contacts 11 are normally open but are closed by the operation of a locking bail |66 which is rocked in counter-clockwise direction by a spring |68 under the control of a cam |61 associated With the cam assembly which controls the operation of transmitting contacts |3. Cam |61 is shown in the rest position and is rotated one revolution for each code combination generated by transmitting contacts |3. This feature is more fully disclosed in Patent 2,018,368, granted October 22, 1935, to R. A. Lake, and particularly in Fig. 5 of that patent. The disclosure of the Lake patent is incorporated herein by reference as part of the present specification. Contacts 11 are closed during the generation of a signal combination by transmitting contacts I3 and therefore during the generation of a modified signal combination by the output relay ||3 of the cipher unit under the joint control of input relay 9 which is controlled by transmitting contacts I3, and the tape controlled signal generator. This disablement of relay 21 is necessary when signals are being generated by relay 36 because otherwise relay 21 would follow the signals so generated, and upon movement of its armature to the spacing position, would complete the energizing circuit for the upper winding of relay 53 over conductor 52. The upper winding of relay 53 when so energized is superior to the lower Winding and will restore the armature to its left-hand position, thus changing the current in the biasing windings of relays 36 and 61 and interfering with the transmission of signals under the control of ciiii' prier -uriit output relay is. Itfwiu be apparent that when signals are being il'n'pressed4 dir upon telegraph' lineY conductors v23 and '24 'through jacks l? and I 3, the relay `21 is not prevented from following thesevsignals and repeating them to the lselector magnet |-2 as previously described, for rth'ereason that jacks 2l and 22 at that 'time have no plug inserted Vtherein and the Ycontacts associated with jack 2| for interconnecting -con-V duc'ters 'I4 and v'I5 are opensc that `the contacts 'il then have no eiiec't upon 'the biasing Winding of'rrelay 21.

It Will be assumed that following the transmissionof 'the start impulse, the irst three message code `ir'npulses generated by transmitting contacts I3 are marking, spacing, marking, and that the rst threes'cip-hering code impulses setup by the tape |32 in v'thesensin'g contacts I3f| fare marking, mark-ing, spacing. Relay 9| Will be restored to its ma king Contact in response to cede impulse to apply negative battery lconnection through its armature to conductor |03. The transmitting contact tongue connected to the rst code segment in the v,outer distributor ring willbe in engagement with its upper or marking con'- the first message tact under the controlofits' tape'sensing pin and Willconneot that segment over conductor H'lto bridg'ecorner IIIa. As the brushes Atraverse the rst 'code segn'ient of the outer ring ofthe dis tiibutor, a circuit may g potentiometer comprising resistors |36 'and |37 through the locking Winding of relay 91x, conductor 134, inner rin'g of `-thedistri'butor, first code segment of the Vouter ring, irs't 'tape `sensing contact vtong-ue and upp'erfor marking contact, conductor'l-lll and in branching paths through resister'l-'If to conductor H19 at bridge-corner `I09o andthrough resistor I| |52, operating Winding of relay |53- andresistor |"|'4 tojconduoto'r`r 109, It will be noted Vthat resistor H4 is now effectively in series with relay A"H3 and resistorfI |2, and resist-or I H" is in parallel with those `three *elements. Current ilows inthe opposite direction through resistors II| and I|4 than it did When the start impulse was 'transmitted and `accordingly the current in the lockingwinding of relay Si during the interval 'that vthe brushes traverse the V`first I'code segment is in 'thej'dir'ecti'o'n to hold the ;armat'ureY of that relay on its marking contact.` The reversal `of the flow of current Ais due to the application of vnegative battery t0 the armature o f relay 9| through its marking Contact instead of the grounded vpositive connection on its spacingV contact. Whereas in 'the case 'of the transmission of the Y cenapletedrfover vco'r'rductor IIS tothe bridge 'corner "I|-"6a,x ithe circuitis now completed 'overcomduct'or Hl to the bridge corner H'lc. Thus the path through 'the operating Winding "of relay H3 t0 the i'lnature and the polarity of battery applied to "the armature ci relay 'Sil 'has Jbeen reversed so `that'the direct-ion of ilovvof -Current through the roperating w'ifri'el-ng'oi relay 5| |13 has not "been changed and its armature remains o n the spacing contact Wherefore the armature of Vrelay SSfremains on its spacing contact and transmits 'as the rst Acode impulse applied to lineV conductors 23 and 2'4, a spacing signal. It may therefore -be stated 'that when transmitting contacts I3 generate `a marking signal and the tape controlled signal generator generates a marking signal, fthe resulting signal transmitted lto the line by-output relay i I3 is a Vspacing signal. It `is also 'to be 'noted that when the transmitting contacts generated. the

be Y"traced 'from the start impulse, Y the circuit was oi relay 9| has been reversed ing position after interruption f through the 'operating Winding of Vgenerated by theftape `'contr 'Vl'g'naturethe dis-5 tributor generated theY equivalent of a vspacing condition independently Vof the tape sensing mechanism; Ydue to theV tacit vthat `v the lstart 'segment lis connected directly 'over conductor |`I6 to bridge corner Hrt-so that the-output relay II3 generated a spacing signal. It is 'apparent firom this that when transmitting contacts 'I3 and the distributor, alone or under the'` control of "tape contacts 13|, generate like signals, whether marking or spacing, lthe resulting signal transmitted to the telegraph line under 'the control `of output relay Y| I3 is o'f spacing natu-re.

It has been assumed that the second code ima pulse generated by transmitting contacts I3 'is Aof spacing nature and that the second code vimpulse generatedrby the 'tape controlled signalgenerator is of marking nature. Input relay `9I of the cipher unit moves to spacing and connects ground to vconductor |03. The circuit Afor the operating Winding of relay I'I 3 is tracedfrom the potentiometer comprising resistors |36 and |31 through the locking Winding of relay 9|, conductor I 34, the inner ring 'of the distributor through the brushes carried by brush arm I 2|, the second code segment in the outer ring, the second transmitting contact tongue Vvvhich engages its upper or marking 'Contact and thence over conductor I'II to bridge corner Illa. The path is the saine as that described in the "preceding paragraph,y

but the polarity on conductor ed positive Vinstead of negativ thus reversing the flow of current through the operating Winding of relay ||3 and driving the armature to the marking contact. The reversed current through the locking Winding of relay 9| during the interval that the brushes traverse the second code segment locks the armature on the to guard against return of the armature to marking position should the "current through the operatingw'inding be changed at this time. The armature of relay `||3 establishes a -ilow of current through the locking Winding of that relay for 'positively holding the armature 'in the mark- `fof the current through the operating Winding, which flows only 'during the brief yinterval that the distributor brushes 'traverse the code segment; The negative or marking battery applied over conductor |56 relay 61,'conduotor `llfail't'fl the Operating'winding of relay 36 moves the armature of the relay'to marking position, ythus r'eolosin'gl the loop across line conductors 23 and 24 for the transmission'of a marking impulse. As Vpreviously stated relay''l does not 'respond a't this time 'to the reversal oi VCurrier-it through its operating `|09 iS now groundposiuon by kits biasing 'winding 4from 'the armature and fight-hand Contact of relay l53. 'It vis obseryedffrom the foregoing that with 'a spacing impulse generated lb'yjthe transmitting contac'ts |73 @and a marking 'i pulse simultaneously oiled signal generator, the-output relay 1rH3 of 'the -cipher unit transmits a niarkin'gnnpulse. v

It Vhas been assumed that the third code 'irnpulse transmitted lby the contacts |3 is of marking 'nature and that the signal generated through the third code Asegment'of the ta-pe controlled 'signal zgenerator is of spacing nature. Relay 9| respondsto the marking signal Igenerated by con-- taots |23 lby moving its 'armature -to the marking position, thus connecting the negative terminalfof respect to relay battery |38 to conductor |09. The circuit for the operating winding of output relay ||3 is now traced from the potentiometer comprising resistors |36 and |31 through the locking winding of relay 9|, conductor |34, inner ring of the distributor, brushes carried by brush arm |2I, the third code segment of the outer ring of the distributor, the third transmitting contact tongue, which is assumed to be engaging its spacing or lower contact, and thence over conductor IIS to bridge corner Ia. By comparison with the circuit ior the operating winding of relay I I3 traced in the preceding paragraph, the circuit branching point is now bridge corner IISa instead of bridge corner II'la, representing a Vreversal with II3, but the battery connection at conductor |09 derived from the armatureY of relay 9| has also been reversed so that the magnetic field in the relay |I3 remains unchanged and the armature remains on its marking contact. The third signal impressed upon the line conductors 23 and 24 is therefore of marking nature. summarizing the transmitting conditions set forth in this paragraph and in the immediately preceding paragraph, when the signals simultaneously generated by transmitting contacts I3 and the tape controlled signal generator are unlike, the signal impressed upon the telegraph line conductor under the control of output relay ||3 is of marking nature. The impulses impressed on the line conductors have been start (spacing), spacing, marking, marking.

The fourth and iifth code impulses will be transmitted to the line conductors 23 andd under the joint control of contacts I3 and the tape con- 2;.

trolled signal generator and thereafter contacts I3 will generate the stop impulse which is of marking nature, thus driving the armature of relay 3| to the marking contact. The brushes carried by brush arm I2I will at this time traverse the stop segment of the outer ring which is connected to conductor IIS. The distributor is thus generating the equivalent of a spacing impulse while the relay 9| has responded to a marking impulse from contacts I3 and since these conditions are dissimilar, the armature of relay ||3 will be moved to the marking position and through relay 36 will impress a marking condition on line conductors 23 and 2d, which is the true stop signal condition.

It will have been noted that when the relay QI responded to the start impulse of spacing nature, relay I I3 was driven to spacing as the distributor traversed the start segment, and that when relay 9| responded to the stop impulse of marking nature, relay I|3 was driven to marking as the distributor traversed the stop segment. It may, therefore, be stated as a part of the theory of operation that only the code impulses are ciphered, as determined by the tape sensing contacts, and that in the case of the start and stop impulses, the start and stop segments are so associated directly with the bridge circuit as to cause relay I|3 to follow relay 9|.

With the relay 9| in the marking position responding to the stop signal from transmitting contacts I3, negative battery is applied over conductors |09 and |131 to the rest segment in the outer ring of the distributor when the two brushes of the brush arm I2| encounter the rest segments and as this battery is oppo-sed by the negative battery |39, start magnet |29 of the distributor is not energized and the brush arm |2| is arrested.

As shown in Fig. 3, the line conductors 23 and 24 extend to a central oice exchange, which has been so labeled in Fig. 3, from which other pairs of line conductors extend to other stations exactly like the one shown in Figs. l and 2, one of which has been shown at the right of Fig. 3 with the several elements labeled in correspondence with the elements of the station shown at the left of Fig. 3 and the latter station is intended to represent the one shown in Figs. 1 and 2. A central office exchange which may be employed for interconnecting telegraph stations in the system according to the present invention is shown in Patent 2,237,154, granted April 1, 1941, to G. A. Locke et al., and the disclosure of that patent is incorporated herein by reference as part of the present specification. Since all of the outlying stations are identical, it has been deemed unnecessary to produce on additional sheets of drawings, a mirror image of Figs. 1 and 2 to describe the operation of a station in receiving signals transmitted from the station shown in Figs. 1 and 2. Instead the operation of receiving a signal will be described with reference to Figs. l and 2 as if the signal had originated at the station shown at the right of Fig. 3 for example. An important fact to be noted regarding the transmission of signals between any two stations in a system such as that shown in Fig. 3 is that the perforated tape |32 shall be identical at all stations and when a connection has been set up through the central oce exchange for intercommunication between two stations in cipher signals, the perforated vtapes shall be placed in the signal generators at the two stations with identical code combinations presented in the tape sensing positions and with identical sequences of signals in storage and awaiting presentation to the tape sensing pins. The manner in which a connection is set up for intercommunication between two stations and the manner in which the use of tapes |32 is agreed upon will be described later.

For the purpose of the following description, it will be assumed that the station shown in Figs. 1 and 2 has ceased transmitting to a remote station and is about to receive signals from the remote station, that the first ciphered signal to be received is identical with that which the station previously transmitted, namely, consisting of a start impulse, a first code impulse of spacing nature, second and third code impulses of marking nature, two unidentified code impulses and a stop impulse of marking nature. This corresponds to the signal the transmission of which by relay 36 has been described heretofore. It will also be assumed that the signal which will be generated by the tape controlled signal generator concurrently with the reception of the signal over telegraph lines 23 and 24 is identical with that, the generation of which was previously described, namely, a start impulse of spacing nature, first and second code impulses of marking nature, third code impulse of spacing nature, fourth and fifth code impulses unidentied and the stop impulse of marking nature.

Due to the fact that transmission from the stations Shown in Figs. l and 2 merely ceased, the relay 53 remains on its right-hand contacts, thus leaving the relay 36 without biasing current and the relay 61 biased in the marking direction so as to be unresponsive to current reversals in its operating winding. Since signals are not being initiated, contacts are opened and normal biasing current is flowing through the biasing winding of relay 21, Seeking to move the armature t0 the spacing position.

The start impulse is received as a no current l condition on the line conductors 23 and 24, to which the line receiving relay 2 responds by moving its armature to .the spacing position. A circuit is -completed from ground through the upper winding of relay 53, conductor 52, spacing contact and armature of relay 21, conductors 48 and 84, middle right-hand armature and back contact of relay V57, conductor 85, marking contact and armature of relay 64, conductor 81, upper closed contacts of jack |18, conductor 88, stationary contact and movable vfront contact operable in make-before-'break manner by the inner right-hand armature of relay 7|, conductor 89, operating winding of cipher unit input relay 9|, to the potentiometer comprising resistors 92 and The current in the upper winding oi relay 53 dominates the armature in spite -of the current through the lower winding vandmoves the armature to the left-hand contact. This removes the ground connection from conductor |-3 extending to the biasing winding of relay 8l', leaving the battery |02 in opposition to the battery 69 through the biasing winding of relay Sl and through the lower winding of relay 53 so that no current flows in this circuit and relay 67 is without bias, thus rendering it responsive to current reversals through its operating winding. Through the armature of relay 53 and its left-hand contact, biasing current is restored to the lower winding of relay 36 and this biasing current is sufhcient to hold the armature of relay 36 on its marking contact irrespective of current reversals through its operating winding.

VIn the relay SI the `effect of the current rsupplied through the spacing contact of relay 2l is to move the armature of relay 9| to the spacing contact, thus reversing the polarity supplied over conductor |47 and through the rest segments oi tape controlled signal generating distributor to start magnet |29, to cause the magnet to beenergized and to release the distributor brush |25 for rotation. The outer brush traverses the start segment which as previously stated is connected over conductor IIS to the bridge corner I ld, and relay ||3 follows relay 9| `to spacing condition. The armature Vof relay IIS connects ground, which is the positivebattery polarity, over conductor A|5Ei through the operating winding of relay t7, conductor |51, operating winding of relay 36 to the potentiometer comprising resistors |58 and |59. Relay St is biased so as to be unresponsive to this reversal of vcurrent but relay 6i now has no current in its biasing windn ing and accordingly the reversed 'current in the operating Ywinding is effective to move vthe arl.

mature to the `spacing position. Before movement of the armature vof relay El to its spacing Contact, current from negative battery t'hrough resistor 58, marking contact and armature'of relay S'I, conductor '85, biasing winding of relay I 64 tothe potentiometer comprising 'resistors '8| and 82 was in a direction Yto cause the biasing winding of relay M to urge the armature to the spacing position but the armature Iwas dominated 'and 'held in the marking 'position by current through the `operating winding from battery 69 through resistor $8, marking contact and -armatureof relay '67, conductor 66, operating Winding ofvrelay 54, conductor 63, back contact and inner left-hand larmature of relay 57,' conductors -62 and 6|,

tip Contact spring of jack 2|, 'tip of the upper plug Section of ydouble plug Irtransinit-'ting conta-cts I 3, tip ci theflower plug section, tip spring of jack 22, conductors 59 and 53, inner right-hand armature and back contact of input relay 9| but is relay 57, conductor 56, sleeve of jack 22, sleeve of the lower plug section of double plug I 4, selectormagnet I2, sleeve of the upper plug section and sleeve of jack 2| to ground. The current 'in this circuit also holds selector magnet I2 energized which is the marlnng condition. With the operation of the armature of relay Yi'l to the spacing position under the control of output 'relay I3, the ground connection on the spacing contact isplaced in opposition to the ground on the sleeve of jack 2|, thus terminating the Aow `of current in the circuit .lust -described including the operating winding of relay'6'4 and the selector magnet I2. The selector lmagnet is thus deenergized which is the spacing condition. The ground connection on the spacing 'Contact of relay 67 also Vreverses the current in the biasing winding of relay 64, so that that winding now urges the armature of relay 64 to remain in 'engagement with the marking contact and since no current flows in the operating winding, this urge is unopposed and the armature remains as stated. The disablement of relay 64 vby reversal of its 'biasing current prevents -it from attempting to `follow the signals applied through its operating winding to selector magnet I2A Were it not for this disablement the armature of relay 64 might go to spacing thus, reoperating relay 53 to its right-hand contact, the eiect of which would be to disable relay 61 and to qualify relay 36 to follow and repeat to the line conductors 23 and 24 signals generated by output relay H3 and intended to operate selector magnet .|2.

Following the 'reception of the start signal, the rst code impulse, which has been presumed to `be of spacing nature, is received and `relay 9| vremains on its spacing contact. The rst code impulse generated by the tape controlled signal generator is assumed to be marking and since this impulse is unlike the received impulse, .relay ||3 goes to marking and reoperates relay 61 to marking, thus reestablishing an energizing circuit for selector magnet |\2-. The signal received by the selector magnet is the reverse of 'that received by like the first code'impulse previously described as having been generated by transmitting contacts I3. The second received code impulse has been 'assumed to be of marking nature, thus restoring relay 9| to its marking contact and the second code impulse generated by the tape controlled signal generator has also'been assumed to Vloe of 'marking nature. This impulse is like the received .impulse and accordingly relay |'|3 goes to spacing and operates relay 61 to spacing which applies a spacing condition to the selector magnet I2. `The third code impulse received has been assumed tobe of marking nature, so that relay 9| remains on its marking contact,

The third code impulse generated bythe tape-con- VYstop segment of erator is connected directly over 'conductor I I6 'tol'bridge corner trolled signal generator has been assumed to be spacing, which is unlike the received code impulse and accordingly relay Vl I3 is operated to its marking contact, operating relay 61 to its marking contact to reestablish the energizing circuit for selector magnet |52. The VVfourth and fth code impulses are thereafter received and selector magnet |2 is operated under the joint control of the cipher unitinput relay 9| and the tape controlled signal generator. The stop impulse is yof marking nature and'operates the relay 8l to its marking condition. As has been previously set forth, the

Vthe tape controlled `signal genfIIBa, to cause relay ||3 to 'be operated to the marking positionunder the Acontrol of relay 3| and selector magnet |2 is ly operated.

It will now be understood that when a signal which has been generated under the control of the transmitting contacts I3 is routed through the cipher unit before transmission, the code impulses are modified by the code impulses of a signal generated by the tape controlled signal generator and a modified signal consisting of a different combination of marking and spacing impulses is transmitted. This modied signal on being received is routed through a cipher unit and is again modified by a signal identical with the rst modifying signal under the control of a tape controlled signal generator whereby the signal is restored to its original condition and will operate a receiving printer to record the character or symbol or to perform the function represented by the key lever which was operated in the keyboard transmitter to initiate the transmission of the signal. It will also be understood that the relay 53 is a reversing relay which is operated to one position or the other, in accordance with whether signals are locally generated for transmission or are received, to reverse cipher unit to the repeater. This reversing control is effected by alternately disabling relay 3B and relay 61, the former being disabled when signals are being received so that signals derived from the output relay not be repeated back into the telegraph line and the relay 51 being disabled when signals are being transmitted so that signals derived from relay i3 will not be repeated back into the local printer circuit. Auxiliary to this reversing control are the controls exercised over the biasing windings of relays 64 and 21 by the armature of relay 61 and the contacts 11, respectively, so that relay E4 will not interpret a spacing signal repeated by relay 61 to the selector magnet |2 as a spacing signal generated by the transmitting contacts |3, and the relay 21 will not interpret a. spacing signal repeated to the telegraph lines 23 and 24 by the relay 36 as a spacing signal received from the telegraph line.

Each station preferably has ringer equipment connected between the telegraph line and the line side of the repeater. The ringer equipment includes ringer |89, condenser |10 in series theresimilarwith, and switch |15. The switch |15, when in the oi or dotted line position, disconnects line conductor 24 from the repeater and connects the ringer and condenser between conductor 24 and ground, which is the shut-down condition, with ringer |59 responsively associated with conductor V 24. When switch |15 is in the on or solid line position, line conductor 24 is connected to the repeater in short-circuiting relation to the ringer and condenser, and ground is disconnected from the ringer.

The procedure for setting up intercommunioation between two stations of the type shown in Figs. l and 2 will now be described. The attendant at the station desiring to communicate with another station inserts double plug |4 into jacks |1 and I8 which aiord the transmission of unciphered signals as previously set forth and operates switch |15 to the on position. An operator at the central office exchange answers the call, due to receiving an indication resulting from operation of switch |15 to the on position, ascertains by telegraph communication with the attendant at the calling station the identity of the called station, sets up the connection and transmits to the called station ringing current to operate the operative relation of the H3 of the cipher unit will f ringer equipment with which each of the stations may be provided. The attendant at the called station answers the call by operating key |15 to the on position and by inserting his double plug into the jack corresponding to jacks |1 and IB which aiord unciphered signal transmission and reception. The attendants at the two interconnected stations may now communicate by direct unciphered transmission and agree upon the eX- act identical points in their tapes |32 which will be placed in their cipher signal generators for the ciphering and deciphering of transmitted and received codes. This having been done, the attendants at both stations remove the double plugs from the jacks |1 and I8 and insert them into the jacks 2| and 22. Thereafter message material may be transmitted back and forth between the two stations and such message material will be in cipher so that if any unauthorized person taps into the telegraph line anywhere between the two interconnected stations with an ordinary receiving printer, orother permutation code recorder,'he will receive ciphered signals which will produce unintelligible printed copy. The lamps 52 and 13 serve to inform an attendant at all times whether the connections and repeater conditions are arranged for unciphered or ciphered transmission and reception.

Reiay 25 (Fig. 2), which has previously been identified as having its winding in series with the operating winding of the line receiving relay 21, has its armature connected to grounded battery |1| and its contact which is engaged by the armature when marking current is flowing in the line conductors 23 and 24 connected by conductors |12 and |13 through the winding of a slow-release relay |14 to ground. Relay 26 follows the signals in the telegraph line and interrupts the energizing circuit for relay |14 when responding to spacing signals but the releasing of relay |14 is suiiiciently slow that it does not release in response to spacing intervals of a duration normally occurring in signal transmission but releases only in response to a long spacing signal such as may be produced by the opening of break key |16 which is included directly in the telegraph line circuit and has been shown in Fig. 2 associated with line conductor 24. The long spacing signal representing the break condition cannot be produced by the operation of break contacts sometimes included in series with the keyboard controlled transmitting contacts of the teletypewriter for the reason that the long spacing signal thus produced would be impressed upon the input relay 9| of the cipher unit and would be ciphered by that unit in accordance with the signal generated by the tape controlled signal generator to cause the transmission by the output relay ||3 of a ciphered signal probably containing marking impulses which would restore the relay 26 to marking and prevent the release of relay |14. By opening the key |16 at either of two interconnected stations for an interval longer than the release time of relay |14, the relay 26 at both stations will go to spacing and remain for a sufcient interval to release their associated relays |14. At the station which has been transmitting and has the armature of its relay 53 on the righthand contact, the relay 21 will respond to the long spacing signal if the transm'tting contacts are then idle or when the contacts open at the end of the code signal then in process oi' transmission, and will move the armature of relay 53 to the left-hand Contact, thereby disabling relay 36 and placing relay 9| (Fig. l) in the steady 19 spacing condition and causing the received long yspacing signal to *be .lciphered and the resulting code signal to be applied to selector magnet :l2

which :has been receiving and has the armature ofits relay 53 on the left-hand\contact, the cipher unitinput relay 9| will respond to the long spacing signal `under 'the control :of line receiving relay 251 v'pending the lrelease of relay 74 vand the lcipher unit will icipher the received long spacing sign-al .only anni relay 114 hasmieased, as avi-libe appar- At its extreme right-hand armature and back contact, relay |14 connects ground supplied through the break contacts of key |f|f'| and foonductor |18 to conductor |13 in :shunt relation to relay |`|2 thus yshont-'circuiting the 'relay so that i-t will not be energized when break key |76 fis connects a closed loop from line conductor 24,

through conductor M92, armature and back contact of relay 11.#4, conductor |83, conductor 28,

2,1 Aiis/hereto the relay 27 :remains operative to 'eceive signals .from the tel graph line .conductors mt relay .36 cannot transmit signals to the line *i :ondu'cton The relay |14 completes a circuit from ground hrough the contacts controlled by jack |`1 which .re closed when plug |11 is not 4inserted :in jacks 1, conductor |84, back contact and arma-ture 'diacent to the outermost rig-holland armature frelay H11, conductors |85, |86 and |8f'|, through ',ounded battery, for operating relay `57. Relay l completes a circuit from ground through vits iter right-.hand armature and front 'contact land rough 'conductor |139 andthe holding winding relay to grounded ibattery 'for holding -the st-m-entioned relay loperated. Relay 51 also mpletes a circuit `from conductor |86 through nductor |91, the outer left-hand 'armature and front contact ci relay 57|, conductor |92, and fthe winding of relay 33 to grounded battery for -energizing relay 33, Relay 33 completes a circuit from ground through its right-hand armature and front contact and through conductor |93 and the holding'winding of relay `5`| for holding that relay energized.

Since the relays 51 Vand 33 are energized in cascade in that order, the operations which they perform -will be described `in the same order. At the inner right-hand armature of relay '1| and front Contact, which has -make-before-'bneak Are lation Ytn a nxed contactJ the negative terminal of battery 96 .is connected lover conductor |194 and conductor 89 extending to the input rela-519| ci the cipher .unit to hold that rela-yin the nia-liking condition and following the completion Ivof this circuit, conductor 88 which eX-tends through oontacts fof Yjack :L8 and conductor 8l t0 the `armature roi relay 64 ,is disconnected `from'conductor 89 so that relay 9| is no longer under the control of Yrelay 611. This chan-ge of vcircuit connections is the same as that whichresults from the operation of the contacts (associated with yjack t8 when .the double plug M is inserted into jacks and i8, and upon the 4occurrence -ol this change the ciphering of the break signal, if lthat signal is still in transmission, W-ill cease -upon lcompletion by the tape controlled signal generator 'of the cycle then in progress. At the left-hand armature -of relay '1| to groun-dconnecticn previously extended Y over the back contact and conductor -'|2 and .through the upper contacts controlled by jack 2| for lighting lamp l5., is removed `from that circuit and is applied over conductor .|95 to lamp 5,2 whereby the lamp becomes lighted and lamp 'I3 becomes extinguished.

At the `middle right-hand armature -of `relay .57, the .conductive path extending from the Iarmature of relay A2'| lover lconducto-rs |8 land 84 is `transferred .from the marking .Contact of relay v(ill to conductor 56 over which a .circuit extends through the sleeve of jack |22, sleeve ofthe `lower plug section of plug |44, .the .selector magnet |12, sleeve of the upper plug section to ground .on the sleeve of Jack .2L This places the selector magnet |2 directly under kthe control of receiving relay 27| and removes it from series relation to the transmitting vcontacts l 3, thus placing the selector magnet l2 in the same relationto receiving relay 21 that it has when plug i4 is .inserted into jacks il and At the inner righ-t and leftfhan'd armatures springs of jacks 2| and 22, vconductive paths are extendedcver conductors L90 andiS respectively, .to line conductor 24 through conductor :47 and to line conductor 23 through the ti-p contact spring and associated Contact of jack Il, through conductors 29 and 28 and the operating windingof These two armatures of relay 51 thus complete the segregation of the circuit of transmitting contacts t3 `from that of selector magnet I2 and establish the same'relationof the transmittingconta-c-ts to the line conductors 23 and 24 that exists when plug |155 is inserted into jacks |"i and A`I 8. It will be noted that the left-,hand armature and backcontact :oi relay LVM are connected by conductors |196 and .|91 to the conductors 59 and 6|, respectively, which extend :to the transmitting contacts I3 so'that the operation of transarmature and back contact of relay |14. At the normally closed contacts which are mechanically operable by the front contact of relay 33, conductor 32 is disconnected from conductol` 34, thus removing the armature of relay 36 from its previous connection to line conductor 23 through conductor 3|, closed contacts of jack I1, conductors 29, 28, and the operating winding of relay 21. At the left-hand armature and back contact of relay 33, the path from contacts 11 to the biasing Winding of relay 21 is interrupted, so that relay 21 will not be prevented from following signals generated by transmitting contacts I3.

From the foregoing, it will be apparent that although the double plug I4 remains in jacks 2| and 22, circuit'changes have been eiected by the relays 33, 51, and 1| to provide for direct unciphered transmission as if plug I4 had been removed from jacks 2| and 22 and inserted in jacks I1 and I8, with the exception that due to the shunt across the transmitting contacts provided by the outer left-hand armature and back contacts of relay |14, the transmitting contacts I3 have been rendered ineffective to generate signals. Also lamp 13 has been extinguished and lamp 52 has been lighted to indicate that the system is now set up for unciphered transmission, Either of the interconnected stations is capable of receiving signals because the receiving relay 21 is effectively associated with the telegraph line conductors 23 and 24 but neither station is now capable of transmitting because of the shunt across the transmitting contacts I3.

Transmission from either of the interconnected stations necessitates the removal of the shunt across the transmitting contacts I3 and thus the reenergization of relay |14. This may be accomplished by operating the key |11 which removes the ground connection which has been short-circuiting the winding of relay |14 through its middle left-hand armature and back contact. In order for the signal transmission to take place in unciphered codes in accordance with the conditions which have been established by relays 33, 51 and 1 I, itis necessary to maintain these relays energized. Accordingly, the make contacts of key |11 are arranged to interconnect conductors |84 and |86 through conductors |98 and |99. The

make contacts, when closed, provide a substitute energizing circuit for relay 33 which in turn holds relay 51 which in turn holds relay 1I. Upon the reenergization of relay |14 from the marking contact of relay 25, the shunt across transmitting contacts I3 is removed and the loop from the line conductor 24 to the left-hand side of the operating winding of relay 21 is removed, The relay 36 is not thereby enabled to impress signals on the line conductors 23 and 24 because the armature has been isolated at the now open contacts mechanically operated by the front contact of relay 33. As a further result of the reenergization of relay |14, lamp |3| is extinguished and the shunt across the make contacts of key |11 at the back contact and armature adjacent to the right-hand armature relay |14 is opened so that the relays 33, 51 and 1I are being held only through the make contacts of key |11. When key |11 is subsequently reclosed, relay |14 will not be again released because the path for shunting its winding is opened at the middle left-hand armature and back contact and the relay can be released only under the control of relay 25.

It is not necessary to operate key I 11 for either of the interconnected stations to receive and 22 record unciphered code signals from the other station but it is necessary to operate the key |11 in order to transmit unciphered code signals. Transmission back and forth between the interconnected stations under these conditions may involve requests for retransmission in cipher of portions previously transmitted in cipher or may convey information that the station which has been receiving has an urgent message for the station which has been transmitting to be transmitted in ciphered code. Before the system is returned to the eiphering condition, the attendants at the two stations should recheck as to the tapes |32 which control their ciphering signal generators and should agree on a resetting' of these tapes as there is a possibility that the tapes at the two stations may get out of step during the transmission of the break signal. When all such intercommunication as is considered permissible to conduct in unciphered codes has been completed, the attendants at the interconnected stations will restore key |11 to normal condition. The restoration of the break contacts has no eiect on the apparatus. The restoration of the make contacts interrupts the holding current for the relays 33, 51 and 1I. Current through the relay 33 and through the operating windings of relays 51 and 1| is at once interrupted. The relays release in the reverse order from that in which they were operated, namely, the relay 33 interrupts the holding circuit for the relay 51 which releases and interrupts the holding circuit for the relay 1| which then releases. As the relays release, they reconvert the repeater connections from those for unciphered transmissions and reception and to those for ciphered signal transmission and reception and they extinguish lamp 52 and relight the lamp 13. Due to the order in which the relays 33, 51 and 1I are .released and due also to the make-before-break relation of certain of their armatures and contacts, no circuit continuities which would, if interrupted, impress momentary spacing signals on the telegraph line conductors 23 or 24 or which might release the distributor of the tape controlled signal generator are disturbed, so that the stations are returned to the cipher code signaling condition with all elements and circuits prepared to cooperate in the transmission or reception of ciphered signals and with the tapes |32 properly in step.

Fig. 4 shows a modified form of cipher unit in which the modication consists in depriving the brush and segment distributor of control over the output relay II3 in connection with the generation by the relay ||3 of a start impulse, and instead placing the relay ||3 solely under the control of input relay 9| for the generation of that impulse. The modification has been accomplished by the addition of apparatus and circuit connections which will be described hereinafter. Fig. 4 fully duplicates the cipher unit apparatus and system shown in Fig. l, and to the extent of such duplication, but disregarding the additional apparatus and circuit connections, the circuit connections of Fig. 4 are identical with those of Fig. 1 except that the distributor has no start segment, so that the only segment in the outer ring of the distributor that is connected directly to conductor I I6 is the stop segment. This has permitted the lengthening of the rest segment either by interconnecting ythe start segment and the rest segment in the outer ring by a conductive strap or by substituting for the rest and start segments in the outer ring a single segment subtending the agenten angle which the two, Aformerly lsubtenii'ed. The 'rest segment `Ain the inner .'ring of the distributor .has not Ibeen lengthened, -from which it will be apparent that Awhen the inner brush leaves Vthe rest segment, the venergizing circuit ,for start magnet Y| 2 9 will beinterrupt'ed, as before.

The apparatus by which relay ||3 has been placed solely under the control of`relay19| or'the yproduction of fstart'impulses comprises polar relay 201| 'having a single Winding, polar winding 202 having operating and biasing windings, normally Aopen contacts 203 Icontrolledbya cam 204 added to vdistributor shaft |122, and :a Vtiming 'condenser '1"206- n One Aend of the 'winding -of relay 20| 'is connected through resistor 1201 to conductor |41, 4and .the "other rend of the winding lis connected to one end of each voff .resistors 203 Vand 209, the other 'ends ci which are 4connected to ground and to the negative terminal of grounded battery, Arespectively, 'and thus form .a potentiometer. Since conductor 141 receives battery connection o negative or positive polarity over conductor |09 as the armature 'of `relay 9| engages 'its marking orA spacing contacts, respectively, :relay `20| will :directly follow `relay S9 I.

The armature of relay'20l 'is `connected through resistor 24| to ground and the marking contact is connected to the right-hand terminal of the operating winding of relay 202,'the other terminal of which is connected through resistor 212 to the negative terminal of grounded battery 2|3. Thebiasi-ng Winding of relay 202 has one terminal connected through resistor 2`|4 to the negative terminal of battery f2|3 and the other terminal connected to ground. Current in the biasing winding of relay 202 seeks 'to move the armature -of Ithat relay `to the left-hand contact, but When the operating Winding of relay 202 is receiving energizing current, that current dominates the armature of relay Y202 and holds it in engagement with the right-'hand contact. The right-hand :terminal ofthe loperating Winding of relay 202 is Ialso connected through variable condenser 200 and resistor 2|6 "to ground. The armature of relay 202 is connected by conductor 2|1 to conductor |34 which extends to the biasing Winding of relay 9| and to the inner ring'oi" the distributor. The left-hand con-tact of relay 202 is connected by conductor 2 I8 to `conductor ||6 which extends to the corner IIEA of the bridge circuit in which the operating Winding of relay H3 is connected.

When relay 9| goes to spacing in response to a start signal generated by the transmitting contacts |'3 or received over the telegraph line, relay 20| also goes to spacing and disconnects ground supplied through resistor 2|| from the operating Winding of relay 202. The operating Winding remains energized due to current which iioWs through resistor '21S for charging the condenser 2706. When the condenser has become charged, the current in the 4operating `Winding of relay 202 dies out and the current in the biasing winding becomes effective to move the armature into engagement with the left-hand contact of the relay. This establishes a conductive path from the potentiometer comprising resistors |36 and |31 through 'the biasing winding of relay 9|, conductors |34 and 2|'|, armature and left-hand contact of relay 202 and conductors 2|'8 and IlfB to the -corner |f|`6A of the bridge circuit, Since the relay 9| is at this time in the spacing condition, the polarities applied across the bridge circuit are such that the armature of relay |13 is moved to the spacing contact to impress a :spacing condition :on the conductor 15.6.

Inthe .iirst Vdescribed embodiment fof :the rinvention, when the armature tof relay 9| moved Yinto engagement with the kspacing contact in response to the start impulse., the venergizing circuit for the start magnet |'29 of the distributor vvas completed, whereby the distributor was 'released fior rotation, and initiated the .transmissionof the start impulse. Since the distributor no longer has a start segment, but only a longer `rest segment, :the generation .of the :start impulse by relay ||3 is not `controlled by the distributor but iis initiated solely under the control -of relay 202. The charging time of condenser i216 and thus the ktime when :the generation of 'the fstart impulse by relay |13 is initiated may be 'varied by varying the capaci-ty :of `condenser 206 .so that if desired, the start :impulse may be initiated before the distributor :brushes could have traveled far enough to engage a start segment if such segment 'were provided on the .distributor as in the previously described embodiment of the invention, or even before the start magnet |29 has become operated. The starting .of the :distributor is the same in the present embodiment of the :invention :as in the vembodiment first described, namely, the reversal y'of polarity on the armature of input relay '9| from which 'a conduct'ive path for energizing start magnet |2=9 is traced `over rconductors |09 and |4'Lrest segments andv brushes of the distributor, and conductor |45 tothe start magnet.

vCam 205 which is secured to distributor shaft |22 presents a low portion Yto the contacts '203 of such length that the contacts l-open about the time that the brushes traverse the stop segment of the distributor, remain open during the rest condition and reclose just before the brushes encounter the first code impulse segment o'f the distributor. One of the springs of contacts 2.03 is connected through conductor '22| and resistor -2 to ground and the other `spring of contacts '203 is connected through conductor 222 lto the righthand side of the voperating Winding vof vrel-ay 202. Thus when contacts 203 are closed 4by cam i200, they reconnect ground to the right-hand terminal of relay 202 through conductor 222, contacts 203, conductor 22| and resistor 2|| so that the operating Winding of relay '292 is reenerg-ized to move the armature of the relay out of engagement with its left-hand Contact, even though relay 20`| may remain on its spacing contact under the control of relay 9|. The interconnection between conductcrs |l and y|30 in shunt relation to the spacing contact side of the tape controlled signal generator which the armature and lefthand contact of relay 202 had established isthus removed before the traversal of the first code segment by the brushes of the distributor, s0 that relay H3 is placed under the control of the distributor during 'the traversal of the code segments and relay 202 is prevented from reoperating to its left-hand contact although relay 20| continues to follow relay 9|. `When the distributor brushes reach the stop segment, at which time relay 9| is 'in the marking condition, -contacts 203 reopen, thus restoring relay 202 to Acontrol by relay 20| which being at this time in the marking condtion holds the voperating 'Winding of the relay 202 energized, and the system is thus prepared for the transmission of the next start impulse.

Although particular embodiments of 'the invention have been disclosed in the ydrawings and described in the foregoing specification, it will be understood that the invention is not limited to such specic embodiment but is capable of modification and rearrangement without departing from the spirit of the invention and within the scope of the appended claims.

What is claimedis:

l. In a telegraph system, a irst signal generator, a second signal generator operable concurrently with said first signal generator, means for interactively combining signals generated by said two signal generators to produce signals diierent from lboth off the interactively combined signals, a telegraph signal receiver, a telegraph line, and means for alternatively associating said cornbining means with said line and said receiver Vin receiving and transmitting relation respectively or with said lirst signal generator and said line in receiving and transmitting relation respectively.

2. In a telegraph system, a message signal generator, a storage type of signal generator having a sequence of non-message signals in storage thereinl a telegraph line, a repeater connected between said message signal generator and said line having a relay responsive to signals generated by said message signal generator and a relay responsive to signals received over said line, means for interactively combining signals generated by said storage type of signal generator and signals yimpressed upon either of said relays to produce signals dilerent from both of said interactively combined signals, and means controlled Yby either of said relays upon response to signals for revers- -in the cooperative relation of said combining 'means to said repeater.

3. In a telegraph system, a message signal generator, a storage type of signal generator having a sequence of non-message signals in storage therein, a telegraph line, a repeater connected between said message signal generator and said line having a relay responsive to signals generated by said message signal generator and a relay responsive to signals received over said line,

means for interactively combining signals generated by said storage type of signal generator and signals impressed on either of said relays to produce signals different from both of said interactively combined signals, and means operable in one predetermined manner by said first-mentioned relay for associating said combining means in signal receiving relation to said first-mentioned relay and operable in a different predetermined manner by said second-mentioned relay for associating said combining means in signal receiving relation to said second-mentioned relay.

4. In a telegraph system, a message signal generator, a storage type of signal generator having a sequence of non-message signals in storage therein, a telegraph recorder, a telegraph line, a repeater connected between said message signal generator and said recorder on one side and said line on the other side, said repeater having a relay responsive to signals generated by said message signal generator and a relay responsive to signals received over said line, means for interactively combining signals generated by said storage type of signal generator and signals impressed on either of said relays to produce signals different from both of said interactively ,combined signals, and means operable in one predetermined manner by said first-mentioned relay for associating said combining means in signal receiving relation to said first-mentioned relay and in signal transmitting relation to said line and operable in a different predetermined manner by said second-mentioned relay for associating said combining means in signal receiving relation to said line and in signal transmitting relation to said recorder.

5. In a telegraph system, a rst source of signals, a second source of signals, a third source of signals, means for interactively combining signals from said first source or said second source and signals from said third source, a signal recorder, means controlled by said combining means for controlling said recorder, a telegraph line, means also controlled by said combining means for controlling said recorder, a telegraph line, means also controlled by said combining means for impressingsignals on said line, and means controlledby signals from said first source for disabling said recorder controlling means and alternatively controlled by signals from said second source for disabling said signal impressing means.

6. In a telegraph system, a station, a rst source of signals thereat comprising a keyboard controlled signal generator, a second source of signals comprising a telegraph line, a third source of signals comprising a storage type of signal generator at said station, means for interactively combining signals from said iirst source or said second source and signals from said third source, a signal recorder at said station, means controlled by said combining means for controlling said recorder, means also controlled by said combining means for impressing signals on said telegraph line, and means controlled by signals from said first source for disabling said recorder controlling means, and alternatively controlled by signals from saidsecond source for disabling said signal impressing means.

7. In a telegraph system, a message signal generator, a storage type of signal generator having a sequence of non-message signals in storage therein, a telegraph line, means for interactively combining signals generated by said two signal generators to produce signals different from both of said interactively combined signals, means controlled by said combining means for impressing said different signals on said line, means for impressing a break signal on said line, and means responsive to said break signal for disassociating said combining means from said message signal generator and for disabling said message signal generator.

8. In a telegraph system, a message signal generator, a storage type of signal generator having `asequence of non-message signals in storage therein, a telegraph lineI means for interactively combining signals generated by said two signal generators to produce signals different from both of said interactively combined signals, means for impressing said different signalsA on said line, means for impressing a break signal on said line, and means responsive to said break signal for disassociating said combining means from said message signalv generator, for associating said message signal generator directly with said line and for temporarily rendering said message signal generator incapable of generating signals.

9. Ina telegraph system, a message signal generator, a storage type of signal generator having a sequence of non-message signals in storage therein, a telegraph line, means for interactively combining signals generated by said two signal generators to produce signals different from both of said interactively combined signals, means for impressing said diierent signals on said line, means for impressing a break signal on said line,

Y means responsive. to. said. break signali for disvassociating. said combining4 means. from said mes.-

sage signal generator, for associating said mes.- sage signal generator directlyl with said line and for temporarily rendering said; message signal generator incapable of generating signals,` and manually operable means for restoring signal generating capability to said message signal gen.-

erator.

l0. In a telegraph system, a. message signal generator, av storage type. ot signal generator having a sequence .'of. non-message signals in storagetherein., a telegraph line, means for interactively combining signals generated by said tivo Signat generators toproducesignals different from both. of. said interactively combined. signals, means. for impressing said: diferentsignals on said line, means for impressing a break signal-'on said line, means; responsive to4 said. break signal for disassociating said combining means. from said. message signal generator, onassociating said message. sgnalgerrerator directly: with said line and for temporarily rendering: saidA message signal generator incapable ci? generating: signals, and manually operable means for' restoring: signal generating capability to. said message signal generator, said.I manually: operable, means being effective uponv restoration to'. normali to. reassociate. said: message signal. generator with. said combining means.

ll.. In. a, telegraph. system, a. message signal generator,` a storage. type. off signal generatorl having: a sequence of non-.message signals in storage. therein, means. for interactively. combining signals generated by.' saidi two signalf. generators to. producel signals. different. from. both'. of said interactively combined signals, a telegraph line, a repeater associated with said. line, means for associating said message signal generator directly with said; line, alternative-lv usable: means vforv associating saidrnessage` signal. generator Withsaid combining means through said'. repeater and for associating said: combining. means with said line through s aidrepeater.

12;. In a` telegraph .systemr av message signal generator', .astoragetype of= signal generator having; aequenceof pong-.message signals; in., storage therein, means for interactively combining signais generated by;- said` two. signal generators. to

produce. signals different fromboth off said interactively combined signals,` ag, telegraph line, a repeater associated with said line, means. for associating saidV message signal. generator directly with said; line. alternatively usable means for associating Said message: signal generator with Said Combining. means; through; saidrepeaterv and for associating saidV Combiningl means. with said line, through said repeater, meansfor impressing abreal,f signal on said line, and means; responsive to said breaksignal whensaid.. alternatively usable means is in use for disassociating said combining means fromY said; message4 signalv gen.- erator and from,l said line and. for.; associating said message signal generator directly: with said line.

143'. In:v a telegraph system, a. message signal generator, a storage typey of: signal generator havin-g ak sequence'v ofv nom-message signals in storage therein, means for interactively combining, signals generated by said two.signa1f generatorsto. produce signals different from both of said interactively combined signals, atelegraph line, a. repeater associated with said line, a recorder, means. for associatingr` saidmessage signal. generator. directly` With said line and' said recorder with said: linev through said repeater, andv alternatively usable'. means for associating saidmessage. signal; generator and said recorder in. seriesv therewith. with said combining means through said repeater and for associating said combining means with said line through said repeater.

14. In a telegraph system, a. message signal generator, a telegraph line, a repeaterl associated with said line, a. recorder, and. switching means for associating said message signal generator' directly with said' line andv saidf` recorder with said line through saidi repeater and for alternatively associating said message signal generator and saidrecorder in series therewith with saldi line through. said repeater.

15. In a telegraph system, a. message signal generator, a storage-type of signal generatorhaving a sequence of Ynon-message signals in. storage. there-in, means. for interactively combining signals generated. by.- said two. signal` generators to. produce signals different. from both of." said interactively combined signals, a telegraph. line, a repeater associated with said line, a. recorder, meansfor associating said message` signal generator directly with` said line and said recorder with said line through. said: repeater, alternatively usable means for associating saidA message signal generator and saidi. recorder in. series therewith with` said combining means through saidY repeater andi for associating said-` combining means; with said. line through said repeater, means' for impressing a break.v signal on said.V line,l and means responsive tosaid break signal. when. said. alternatively usable means is inuse=f-or dissassociating said combiningv means from: said messageL signal generatork andi from4 said. line and; for associating said message signal: generator directly4 with. said lineand said recorder with said linethrough-said repeater.

161.111. a telegraph. system, a messageA signal ,A genera-tor, a telegraph line, arepeater associated with .said line, a recorder., means forassociating saidi message'l signal'. generator' directly.` with said line and' saith recorder with; said. line through.` said repeater, alternatively.v usable means, for associating sai'd?. message signal generator and said recordenin' serestherewithwith saidline=through said repeater, meansifor impressing a break sig'- ria-1LV on.` said line, and'.` mean-s: responsive` to. said break signal. when. said. alternatively usable meansisain.l use: for" associating.1 saidi message. siginal: generator. directly.Y vvitl'r` said?. line; andy said recorder with said: line through. said: repeater.

17. InA atel'egraphsystem, a. message; signal generator for generating.. startestop telegraph signals element by elementrjnisuccession, astor.- age; type: signal:4 generator.- havingi a. sequence ofinommessage signals-,imstoragetherein for gen.- eratingf telegraph: signals element by. element in succession, a telegraph line, means.A for interactively.) combining: signal'A elementsggenerated by saidtwol Signal'. generators; andi means. corrtrolledi by.: said combining; means; fer" activating said. storage. typeL of signal? generatorh inI startstop-mannen for each; signal. generating: cycleL of said message signal generator:

18. In a telegraphk system; al message signal generatorl` for.- generating startestop; telegraph signals elementy by) element: in succession; a fir-st single relayI responsive tosaidA` signa-1`- elements, a storage-- type` of;` signalA generator having; a

f sequenceofnon-message signalsvin'storagetherely b-y` said iirst single relay and said storage type of signal generator for interactively combining signal elements generated by said message signal generator with signal elements generated by said storage type of signal generator, and means controlled by said rst single relay for activating said storage type of signal generator in start-stop manner for each signal generating cycle of said message signal generator.

19. In a telegraph system, a message signal generator, a storage type oi signal generator having a sequence of non-message signals in storage therein, a telegraph line, means for interactively combining signals generated by said two signal generators to produce signals dierent from both of said interactively combined signals, means for impressing said diierent signals on said line, means for impressing a break signal on said line, and means responsivey to said break signal for disassociating said combining means from said message signal generator, for connecting said message signal generator directly to said line and for temporarily shunting said line against control by said message signal generator.

20. In a telegraph system, a message signal generator, a storage type of signal generator having a sequence of non-message signals in storage therein, a telegraph line, means for interactively combining signals generated by said two signal generators to produce signals different from both of said interactively combined signals, means for impressing said different signals en said line, means for impressing a break signal on said line, means responsive to said break signal for disassociating said combining means from said message signal generator, for connecting said message signal generator directly to said line and for temporarily shunting said line against control by said message signal generator, and manually operable means for disabling said shunting means.

21. In a telegraph system, a message signal generator for generating start-stop telegraph signals impulse by impulse in succession, a storage type of signal generator having a sequence of non-message signals in storage therein for generating signals element by element in succession, a telegraph line, means for interactively combining signals generated by said two signal generators to .produce signals different from both of said interactively combined signals, means controlled by said combining means for activating said storage type of signal generator in startstop manner for each signal generating cycle of said message signal generator, and means for causing said combining means to produce the start impulses of said different signals independently of said storage type signal generator.

22. In a telegraph system, a message signal generator for generating start-stop telegraph signals, a storage type of signal generator having a sequence of non-message signals in storage therein, a telegraph line, means for interactively combining signals generated by said two signal generators to produce signals diiierent from both of said interactively combined signals, means controlled by said combining means for activating said storage type of signal generator in startstop manner for each signal generating cycle of said message signal generator, means for causing said combining means to produce the start impulses of said diierent signals independently of said storage type signal generator, and means for varying the time of initiation of 30 said start impulses relative to the activation of said storage type of signal generator.

23. In a telegraph system, a message signal generator for generating start-stop telegraph signals element by element in succession, a first single relay responsive to said signal elements, a storage type of signal generator having a sequence of non-message signals in storage therein for generating signals element by element in succession, a second single relay controlled jointly by said rst single relay and said storage type of signal generator for interactively combining signal elements generated by said message signal generator and signal elements generated by said storage type of signal generator, means controlled by said rst single relay for activating said storage type of signal generator in startstop manner for each signal generating cycle of said message signal generator', and means controlled by said first single relay for causing said second single relay to generate the start impulses of said different signals independently of said storage type of signal generator.

24. In a telegraph system, a message signal generator for generating start-stop telegraph signals element by element in succession, a rst single relay responsive to said signal elements, a storage type of signal generator having a sequence of non-message signals in storage therein for generating signals element by element in succession, a second single relay controlled jointly by said rst single relay and said storage type of signal generator for interactively combining signal elements generated by said message signal generator and signal elements generated by said storage type of signal generator, means controlled by said first single relay for activating said storage type of signal generator in startstop manner for each signal generating cycle of said message signal generator, means controlled by said iirst single relay for causing said second single relay to generate the start impulses of said different signals independently of said storage type of signal generator, and means for varying tbe time of control of said second single relay by said last-mentioned means relative to the time of activation of said storage type of signal generator.

' 25. In a telegraph system, first means for generating signal combinations each comprising a succession of impulses, second means for concurrently generating signal combinations each comprising a succession of impulses, means for interactively combining corresponding impulses of said concurrently generated code combinations, a telegraph line, and means for causing impulses resulting from said interactive combination of impulses to be impressed on said line.

26. In a telegraph system, means for generating signal combinations in a sequence oomprising a message, each signal combination comprising a succession of impulses, means for concurrently generating signal combinations in a random sequence, each signal combination comprising a succession of impulses, means for interactively combining corresponding impulses of said concurrently generated code combinations, a telegraph line, and means for causing impulses resulting from said interactive combination of impulses to be impressed on said line.

27. In] a telegraph system, first means for generating signal combinations comprising impulses succeeding one another at predetermined intervals, second means for generating signal encaisse Jmbinations comprising impulses succeeding one nother at predetermined. intervals. means for. iteractiyely combining; impulses generated in crresponding intervals by' said rst and second :gnat` generating means. a` telegraph. lina. and leans for causing impulses resulting from said iteractive. combination of: impulses to bev imressed on said line.

28..In a telegraph system, means for gener.- ting signal combinations inasequence comprise 1g; a message, each signal'. combination compris- .'ig impulses.v succeeding oney another at. predeermined intervals, means for: generating signal ombinations in a random sequence; eachsignal ombinati'on comprising impulses succeeding, one nother at predetermined. intervals,l means for ateractiyely combiningl impulses generated in orresponding intervals by' said. two. signal genrating means,. a. telegraph line, and, means for ausing impulses. resulting from said. interactive ombination oi impulses td be; impressed on said Lne.

29. In atelegraph system, rst means,- for genrati'ng signal combina-tions; comprising impulses ucceeding one` another at predetermined interfals', second means for generating signal cominations comprising impulses succeeding. one` anther at predetermined intervals, means for inera-ctively combining impulses generated in coryesponding intervals by said. iirst and second ignal generating means. during the: generation if; said impulses, a telegraph line, and means 'or causing impulses resulting from. said. nterictive combination of impulses. to. be impressed n said line.

30. In. a. telegraph system, a. telegraph. line, a golargrelay having an operating. Wind-ing',.a bridge tircuit connected across said. operating Winding, neans for selectively connecting an electrical )otential of either of two. polarities to the mide aoint of; said bridge; circuit, means for selectively :onnecting the return path for said electrical potential to either of the common terminals of. ;aid operating winding and said bridge circuit, ind meansV controlled by said relay for'impressing ;ignaling impulses on said line.

3l. In a telegraph system,. a telegraph; line, a colar relay having an operating Winding-a bridge circuit connectedv across said operati-ng winding, a; telegraph signal generator adapted tof cause an. electrical potential of either' of two-polari-ties to be; connected to the. mida-point of said bridge circuit, a second telegraph signal generator adapted. to connect; a return path for' said'. electrical potential to either of the: common terminals of, said operating winding and said bridge circuit, and means. controlled byA said: relay for impressing signaling. impulses on said line.

32. In a telegraph system,. a. telegraph'. line, a polar relay having: anoperating winding, a bridge circuit connected across. said Winding, means for generating telegraph signals representing a mes'- sage. adapted to cause an electrical potential of either of tivo polarities to, be connected to the mid-point: of said. bridge circuit, means for generatin'g telegraph signals representing a. random sequence of codes adapted. to connect a return path foi-said electrical potential to either of the common terminals ot said operating winding and said; bridge: circuit.. and means controlled by' said relay for impressing signaling? impulses' on. said lines..

335.- In. a telegraph system a telegraph line, a, polar relay having an operating Winding a bridge circuit connected across said operating Winding, a source of electrical potentialof either of tWo polarities and a returny path therefor, selectively operablemeans. for causing current to flow at either'o'f said polarities through said operating Winding and bridge circuit and return path,

selectively operable means for causing' each of.

said currents to iiow in either direction through said operating Winding, and means, controlled by said relay forv impressing signaling impulsesy on said line'.

34. In a telegraph systenn a Atelegraph line, a polar relay having an operating winding, a bridge circuit connected across said operating Winding', a source of. electrical potential of either of two pclarities and. a return path therefor, means for generating telegraph signals representing a message` adapted to cause current to flow at either of said polarities through said operating Winding and bridge circuit and return path', meansl for generating telegraph signalsrepresenting a ran'.- dom` sequence of codes adapted to cause each of said: currents to` iiow in either direction through said operating Winding. and means controlled by said relayl for impressing signaling impulses on. said. line.

KARL E. FITCH. GEORGE A.y LOCKE. 

